Rep. Tammy Duckworth ended a political guessing game Monday by making it official that she is exploring a challenge to Sen. Mark Kirk in 2016.

Duckworth, a Democrat from Hoffman Estates, told the Tribune she is considering a bid against the Highland Park Republican, raising the potential of a high-dollar campaign between two military veterans known for their comebacks.

Kirk recovered from a major stroke in 2012.

Duckworth came back from losing her legs in the Iraq War in 2004 when the Black Hawk helicopter she was piloting was hit by a rocket-propelled grenade. Defeated in her first try for Congress in 2006, she captured a House seat in 2012.

Kirk is the more experienced politician. He entered the House in 2001 and the Senate in 2010. He's won a statewide race only once, and narrowly, against a Democratic candidate with baggage: Alexi Giannoulias, then state treasurer.

The Democratic nominee for Senate in 2016 is likely to be buoyed by the Democrat at the top of the ticket. It's a presidential election year, and Illinois voters last favored a Republican for the White House in 1988.

Duckworth had been considered a potential candidate even before Monday, when she told the Tribune: "I'm humbled by the encouragement that I'm receiving to run for the Senate, and it's pretty clear that people are looking for a change, and I'm going to explore the possibility."

Illinoisans, she said, "want someone who will actually get some work done." She singled out immigration reform, making college more affordable, raising the minimum wage and helping manufacturers.

A statement from the Kirk camp said the senator was an "independent voice for Illinois" who was proud of his "bipartisan record of achievement." Kirk is focused on fighting for veterans and spurring economic growth and job creation, the statement said.

Duckworth, 46, gave birth to her first child Nov. 18 and said she wanted her baby to be 2 months old before she took a serious look at the race. She is on maternity leave until Feb. 16 and will not attend Tuesday's State of the Union address.

Kirk, 55, retired as a commander in the Navy Reserve in May 2013 and last year vowed to seek re-election "come hell or high water."

Talking about a potential challenge from Duckworth, he told The Hill last fall: "To fight and lose a Senate race against Kirk is a terrible start to a career."

Duckworth, asked Monday about Kirk's remark, thanked the senator for his interest in her career and noted that he would not be among those she consults before making a decision on whether to get in the race.

Kirk's race has been called a tossup by political scientist Larry Sabato's Crystal Ball at the University of Virginia and The Rothenberg & Gonzales Political Report in Washington.

Sabato, in an interview, said Illinois Democrats may prefer Illinois Attorney General Lisa Madigan — with her dominant political name — as a challenger to Kirk, but noted she's turned down a chance to run for Senate before. She still could throw her hat in the ring, he said.

He thinks it will be tough for Kirk in 2016 to pick up enough crossover votes from Democrats to prevail in light of the presidential race.

The Senate contest in Illinois will be heavily watched since Kirk's seat is a pickup Democrats need, as they do in Wisconsin and Pennsylvania, if they have any hope of regaining the Senate, he said.

Rothenberg & Gonzales said only two Senate races in 2016 — in Illinois and Wisconsin — were "pure toss-ups."

Editor and publisher Nathan Gonzales said Duckworth has been part of the Democratic narrative since she unsuccessfully challenged Rep. Peter Roskam, R-Ill., in 2006.

"She has a lot of allies and friends who are encouraging her and would like to see her run," Gonzales said. "Her story has captured a lot of Democratic activists and donors and strategists."

Gonzales said that there would be limitations on Kirk being able to get around the state to campaign in light of his health but that retail politics matter less in Illinois than in smaller states. "This is going to be about raising a massive amount of money and getting on television to make your case," he said.

Most recent campaign finance reports showed Duckworth with more than $1 million in her war chest and Kirk with $1.5 million.